Microfluidic devices have tremendous potential for applications in a variety of fields including drug discovery, biomedical testing, and chemical synthesis and analysis. In such devices, liquids and gases are manipulated in microchannels with cross-sectional dimensions on the order of tens to hundreds of micrometers. Processing in such microchannel devices offers a number of advantages including low reagent and analyte consumption, highly compact and portable systems, fast processing times, and the potential for disposable systems. However, in spite of all of their promise, microfluidic devices are currently being used in a limited number of applications and are in general still rather simple devices in terms of their operational complexity and capabilities. One reason for their limited use is the difficulty in forming microchannels having a defined form.
For example, fluid microdynamics through the microchannels is important to avoid mixing in systems where mixing is not needed and therefore, the microchannels should have a defined cross-section consistent with the fluid microdynamics needed. However, fabricating a defined cross-section can be challenging. For example, the selection of sacrificial polymers and overcoats used to fabricate the microchannels can be limited due to solvent incompatibility of the sacrificial polymer and the overcoat. If the overcoat solvent dissolves the sacrificial polymer, the shape defined by the sacrificial material is compromised. In addition, the overcoat layer should provide sufficient mechanical strength to span the dimensions of the airchannel without sagging. Therefore, there is a need in the industry for versatile techniques to fabricate defined microchannels using a wider variety of polymer combinations.